Building a new home..2 units OR 1 unit with zoning? Newbie needs help..

[George2]

I vote for one system.
If you know how to design, then it should not be a problem with only one system, especially when you mentioned a dual-fuel set up... you have your backup already built-in!
Why two, it's not very green or cost effective? More energy is used up and each system will probably be oversized a bit due to the equipment limited small sizes manufactured.

If your serious, then forget the equipment in the attic idea. Sized the duct/s correctly, never ovesize, and seal everything: ducts, house etc...
and don't forget a good fresh-air system....

Note: the only time I would install two systems is when they need more than 5 tons of cooling.

Normally I would go with one system except he's thinking of using heat pump(s). One (1) five ton (approx. 45,000 Btus) HP won't do him much good. He'll be on back up (electric) heat all the time.

[garyed]

Zoning co$t is NOT Negligible. I am not a contractor, but - one might guess that zoning $$$ might be 'in the range
of half' of a second system. So, ... where's the Real savings __ only 'A FEW $$$'s' in the builder's pocket.?! ...................

When I said the savings is minimal I was comparing it to the cost of buildning a whole house. If it costs 20% less to do a zone sytem & the HVAC costs afre 5% of the cost of building the house then we're only talking about 1% of the total cost & probably even less than that. The only reason builders like to do one zone system is so they can cut costs plain & simple. It has nothing to do with what is best for the house. If the HVAC guy told them it would cost more to do one zone system then the builder would recommend two separate systems.

[dan sw fl]

The only reason builders like to do one zone system is so they can cut costs plain & simple. It has nothing to do with what is best for the house. If the HVAC guy told them it would cost more to do one zone system then the builder would recommend two separate systems.

LESSON LEARNED ... ALWAYS TELL BUILDER a single system With Zoning
is MORE expensive due to planning, dampers, EXTRA Ducting + amount of labor.

[lithnights]

A1: I would venture to say that you would get two systems, and two would be the better design than one system for a few reasons.

A2: NOT ONLY YES, BUT HELL YES!

Just like anything else, get a second opinion (and maybe a third), and see if you can get two (or may three) matching designs.

There is a lot that goes in to a system to make sure you achieve optimum comfort control.

When building, the biggest thing you can do to ensure you achieve optimum comfort control is: don't skimp on the insulation, and windows and doors.

I don't care how great your system is, with out proper insulation, and good window and doors you are pissing in the wind.

Please watch this video, one of the best ones out there imo.

So when you say 2 would be better for a number of reasons, what would they be?

Regarding the 2nd/3rd opinions, how would one do that if the builder is in charge of the HVAC and uses a certain HVAC sub? Does one ask them to go out and get a 2nd opinion, or does the homeowner find that 2nd opinion?

I agree, insulation is key. I am upgrading the Silverline (by Andersen) windows to Andersen 200 series. I am planning on doing 2 inches of spray foam throughout the exterior and attic floor. The house is 2x6 (not 2x4). I am planning on having R50 or so in the attic.

[lithnights]

I would probably opt for 2 separate systems to keep the air noise down (two 3 ton vs one 5 ton blower). I like geothermal system(s) but I also like the foam insulation. I would do some load calculations (to find the payback) as to the best bang for the buck.

Remember, the better insulated home requires smaller HVAC. So the extra money spent on insulation saves on the cost of the HVAC equipment.

I looked into geothermal but I simply can't afford it (even with the federal tax credit and the long term savings). Doing the spray foam based on the builder's cost estimates.

[lithnights]

One other thought........I would keep all a the HVAC out of the attic. Equipment and ductwork.

If not in the attic, then both units in the basement?

[lithnights]

I vote for one system.
If you know how to design, then it should not be a problem with only one system, especially when you mentioned a dual-fuel set up... you have your backup already built-in!
Why two, it's not very green or cost effective? More energy is used up and each system will probably be oversized a bit due to the equipment limited small sizes manufactured.

If your serious, then forget the equipment in the attic idea. Sized the duct/s correctly, never ovesize, and seal everything: ducts, house etc...
and don't forget a good fresh-air system....

Note: the only time I would install two systems is when they need more than 5 tons of cooling.

I agree, if one knows how to design.. unfortunately I don't, so I'm dependent on the HVAC feedback to the builder. : )

I guess we'll soon find out if I need more than 5 tons of cooling..

[lithnights]

When I said the savings is minimal I was comparing it to the cost of buildning a whole house. If it costs 20% less to do a zone sytem & the HVAC costs afre 5% of the cost of building the house then we're only talking about 1% of the total cost & probably even less than that. The only reason builders like to do one zone system is so they can cut costs plain & simple. It has nothing to do with what is best for the house. If the HVAC guy told them it would cost more to do one zone system then the builder would recommend two separate systems.

This is exactly what I'm afraid of. And unlike many scenarios I run into in life, it's difficult for ME to research/analyze and try to come up with the best solution on my own.

[mogy]

all contractors should run a Manual J to properly to identify what system size you should start with. From there I would decide two systems vs. one with zoning. Something else to think about when it comes to a new home is indoor air quality. Start by installing a good 4" filter at the unit. Then way the cost between a base builder grade efficient HVAC system with options for higher efficient ones. I would recommend an indoor unit with a variable speed blower, even the newer non-variable speed ECM blowers are better than a standard blower. When you look at upgrading efficiency and IAQ sometimes the cost to upgrade two vs. one is a factor. A good contractor will help you with your budget, utility consumption and provide comfort and a healthier home.

Get that manual j from your builder from all HVAC contractors and make sure they print out a long form so you can review it and that it follows ACCA standards.

[dan sw fl]

I agree, if one knows how to design.. unfortunately I don't, so I'm dependent on the HVAC feedback to the builder. : )

I guess we'll soon find out if I need more than 5 tons of cooling..

3 tons could be TOO Much for proper Thermal Envelope.
You didn't read reply provided in post #6.

Spray foam is recommended for the Underside of the roof.
http://www.buildingscience.com/docum...r-all-climates

ALL DUCTS IN CONDITIONED SPACE.

I guess if you don't control the design and installation,
You Get what You Get
and DON.T Have a Fit.

[George2]

If not in the attic, then both units in the basement?

I've done 2 systems in homes keeping both in the basement and I've had builders but the utility room on the second floor. With todays taller ceilings the ductwork can stay out of the attic.

[lithnights]

all contractors should run a Manual J to properly to identify what system size you should start with. From there I would decide two systems vs. one with zoning. Something else to think about when it comes to a new home is indoor air quality. Start by installing a good 4" filter at the unit. Then way the cost between a base builder grade efficient HVAC system with options for higher efficient ones. I would recommend an indoor unit with a variable speed blower, even the newer non-variable speed ECM blowers are better than a standard blower. When you look at upgrading efficiency and IAQ sometimes the cost to upgrade two vs. one is a factor. A good contractor will help you with your budget, utility consumption and provide comfort and a healthier home.

Get that manual j from your builder from all HVAC contractors and make sure they print out a long form so you can review it and that it follows ACCA standards.

I have read some about variable speed, in fact was at one point looking at the Greenspeed unit. Even if I don't do that specific unit, I do want to get a more efficient, and overall better, unit even if it does cost a bit more. I will be sure to ask for the manual J printout.

[lithnights]

3 tons could be TOO Much for proper Thermal Envelope.
You didn't read reply provided in post #6.

Spray foam is recommended for the Underside of the roof.
http://www.buildingscience.com/docum...r-all-climates

ALL DUCTS IN CONDITIONED SPACE.

I guess if you don't control the design and installation,
You Get what You Get
and DON.T Have a Fit.

I did read the reply in post #6 but don't see where it mentioned that 3 tons could be too much. Am I missing something?
I'll be sure to look into spray foam for the roof underside.